U.S. patent number 10,001,149 [Application Number 14/502,241] was granted by the patent office on 2018-06-19 for manufacturing soft devices out of sheet materials.
This patent grant is currently assigned to PRESIDENT AND FELLOWS OF HARVARD COLLEGE. The grantee listed for this patent is President and Fellows of Harvard College. Invention is credited to Kevin C. Galloway.
United States Patent |
10,001,149 |
Galloway |
June 19, 2018 |
Manufacturing soft devices out of sheet materials
Abstract
A soft composite actuator is described, including a first
elastomeric layer; a strain limiting layer; and a first radially
constraining layer, wherein the first elastomeric layer is disposed
between the first radially constraining layer and the strain
limiting layer; and the elastomeric layer, the strain limiting
layer, and the radially constraining layer are bonded together to
form at least one bladder for holding pressurized fluid. Methods of
using and making of the soft composite actuator are described.
Inventors: |
Galloway; Kevin C. (Somerville,
MA) |
Applicant: |
Name |
City |
State |
Country |
Type |
President and Fellows of Harvard College |
Cambridge |
MA |
US |
|
|
Assignee: |
PRESIDENT AND FELLOWS OF HARVARD
COLLEGE (Cambridge, MA)
|
Family
ID: |
52738820 |
Appl.
No.: |
14/502,241 |
Filed: |
September 30, 2014 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20150090113 A1 |
Apr 2, 2015 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
61885092 |
Oct 1, 2013 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B25J
9/142 (20130101); B25J 15/10 (20130101); B25J
15/08 (20130101); B25J 15/12 (20130101); F15B
15/10 (20130101); B25J 15/0023 (20130101); F15B
15/103 (20130101); Y10T 156/10 (20150115) |
Current International
Class: |
B25J
15/00 (20060101); B25J 15/08 (20060101); F15B
15/10 (20060101); B25J 15/10 (20060101); B25J
9/14 (20060101); B25J 15/12 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
19617852 |
|
Oct 1997 |
|
DE |
|
1319845 |
|
Jun 2003 |
|
EP |
|
1512703 |
|
Jun 1978 |
|
GB |
|
2006204612 |
|
Aug 2006 |
|
JP |
|
WO-2012/148472 |
|
Nov 2012 |
|
WO |
|
WO-2012150551 |
|
Nov 2012 |
|
WO |
|
WO-2013015503 |
|
Jan 2013 |
|
WO |
|
WO-2013110086 |
|
Jul 2013 |
|
WO |
|
Other References
International Search Report and Written Opinion for International
Application No. PCT/US14/58244 dated Jan. 2, 2015. 11 pages. cited
by applicant .
European Search Report issued in application No. 14851387.2, dated
Jun. 14, 2017, 9 pages. cited by applicant.
|
Primary Examiner: Kraft; Logan
Attorney, Agent or Firm: Wilmer Cutler Pickering Hale and
Dorr LLP
Government Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
This invention was made with government support under DARPA Grant
No. N66001-13-C-4036 awarded by the Department of Defense. The
United States government has certain rights in this invention.
Parent Case Text
RELATED APPLICATION
The present application claims priority to U.S. Provisional
Application 61/885,092, filed Oct. 1, 2013, which is hereby
incorporated by reference in its entirety.
Claims
I claim:
1. A soft composite actuator, comprising: a strain limiting layer;
a first radially constraining layer; and a first elastomeric layer
disposed between the first radially constraining layer and the
strain limiting layer; wherein the first elastomeric layer, the
strain limiting layer, and the first radially constraining layer
are bonded together to form at least one bladder for holding
pressurized fluid; and the radially constraining layer comprises
one or more openings through which one or more portions of the
first elastomeric layer expand upon actuation, and one or more
strain limiting sections free from any openings.
2. The soft composite actuator of claim 1, the bond is selected
from the group of thermal bonds, chemical bonds, mechanical bonds
and combinations thereof.
3. The soft composite actuator of claim 1, wherein the soft
composite actuator further comprises a second elastomeric layer
disposed adjacent to the first elastomeric layer and the strain
limiting layer comprises a second radially constraining layer.
4. The soft composite actuator of claim 1, wherein the radially
constraining layer comprises one or more radially constraining
sections.
5. The soft composite actuator of claim 4, wherein the radially
constraining sections comprise radially constraining strips evenly
or unevenly distributed in the radially constraining layer.
6. The soft composite actuator of claim 5, wherein the radially
constraining strips are oriented parallel to one of the edges of
the radially constraining layer or at an angle to one of the edges
of the radially constraining layer.
7. The soft composite actuator of claim 5, wherein the radially
constraining strips are bonded to the first elastomeric layer.
8. The soft composite actuator of claim 1, wherein the first
elastomeric layer, the strain limiting layer, and the first
radially constraining layer are bonded together to form a plurality
of bladders for holding pressurized fluid.
9. The soft composite actuator of claim 1, wherein the soft
composite actuator further comprises one or more rigid elements
attached to the strain limiting layer.
10. The soft composite actuator of claim 1, wherein the bladder is
designed to accommodate a pressurized fluid selected from the group
consisting of a gas and a liquid.
11. The soft composite actuator of claim 1, wherein one of the
elastomeric layer, the strain limiting layer, and the radially
constraining layer is configured to absorb fluids, transmit light,
change color or luminescence, embed a soft sensor or a medical
patch, embed at least a part of an electronic circuit or a heating
element, or a combination thereof.
12. The soft composite actuator of claim 1, wherein the soft
composite actuator is part of a splint, a grasper, or a glove
comprising a plurality of digits, or is a splint, a grasper, or a
glove.
13. A soft actuating device comprising a plurality of the soft
composite actuators of claim 1.
14. The soft actuating device of claim 13 comprising: a first soft
composite actuator connected to a first fluid source; and a second
soft composite actuator connected to a second fluid source.
15. A method of actuation comprising: providing the soft actuating
device of claim 14; and pressurizing the first soft composite
actuator's bladder and the second soft composite actuator's bladder
alternately by activating the first fluid source and the second
fluid source alternately.
16. The method of claim 15, wherein the first soft composite
actuator bends upon actuation and the second soft composite
actuator stiffens upon actuation.
17. A method of actuation comprising: providing the soft actuating
device of claim 13; and pressurizing one or more bladders with one
or more fluids, wherein the soft actuating device actuates in a
predetermined manner.
18. A method of making a soft composite actuator of claim 1,
comprising: providing a first elastomeric layer, a strain limiting
layer, and a first radially constraining layer; wherein the
elastomeric layer is disposed between the radially constraining
layer and the strain limiting layer; and bonding the first
elastomeric layer, the strain limiting layer, and the first
radially constraining layer to form sealed parameters defining at
least one bladder for holding pressurized fluid.
19. The method of claim 18, wherein providing a first elastomeric
layer, a strain limiting layer, and a first radially constraining
layer comprises: providing a pre-stacked laminate comprising a
first elastomeric laminate layer, a strain limiting laminate layer,
and a first radially constraining laminate layer; and separating
part of the laminate to provide the first elastomeric layer, the
strain limiting layer, and the first radially constraining layer
stacked together.
20. The method of claim 18, wherein the bond is selected from the
group of thermal bonds, chemical bonds, mechanical bonds and
combinations thereof.
21. The method of claim 18, wherein the elastomeric layer, the
strain limiting layer, and the radially constraining layer are
contained in a package.
22. The method of claim 21, wherein bonding is achieved by external
heat passing through the packaging or internal heat generated by a
heating element inside the packaging without the compromise of the
package.
23. The method of claim 18, wherein the elastomeric layer or the
first composite layer is in a pre-strained state before
bonding.
24. The method of claim 18, wherein one of the layers has a
non-planar shape before or during bonding.
25. A soft composite actuator, comprising: a first composite layer
having a length and a width comprising one or more first
elastomeric sections and one or more first radially constraining
sections that traverse the width of the first composite layer; and
a second composite layer having a length and a width comprising one
or more second elastomeric sections and one or more second radially
constraining sections that traverse the width of the second
composite layer; wherein the first composite layer and the second
composite layer are bonded together to form at least one bladder
for holding pressurized fluid, and wherein the radially
constraining sections constrain radial expansion of the bladder and
the elastomeric sections allow expansion of the first and second
composite layers along their lengths.
26. The soft composite actuator of claim 25, wherein the first and
second composite layers have the same thickness.
27. The soft composite actuator of claim 25, wherein upon actuation
the first and second composite layers expand to extend the actuator
a distance along the length of the bladder.
28. The soft composite actuator of claim 25, the bond is selected
from the group of thermal bonds, chemical bonds, mechanical bonds
and combinations thereof.
29. The soft composite actuator of claim 25, wherein the radially
constraining sections comprise radially constraining strips
oriented parallel to one of the edges of the composite layer or at
an angle to one of the edges of the composite layer.
30. The soft composite actuator of claim 29, wherein the radially
constraining strips are evenly or unevenly distributed in the
composite layer.
31. The soft composite actuator of claim 25, wherein the first
composite layer and the strain limiting layer are bonded together
to form a plurality of bladders for holding pressurized fluid.
32. The soft composite actuator of claim 25, wherein the soft
composite actuator further comprises one or more rigid elements
attached to the strain limiting layer.
33. The soft composite actuator of claim 25, wherein the bladder is
designed to accommodate a pressurized fluid selected from the group
consisting of a gas and a liquid.
34. The soft composite actuator of claim 25, wherein one of the
layers is configured to absorb fluids, transmit light, change color
or luminescence, embed a soft sensor or a medical patch, embed at
least a part of an electronic circuit or a heating element, or
combination thereof.
35. The soft composite actuator of claim 25, wherein the soft
composite actuator is part of a splint, a grasper, or a glove
comprising a plurality of digits, or is a splint, a grasper, or a
glove.
36. A soft actuating device comprising a plurality of the soft
composite actuator of claim 25.
37. A method of actuation comprising: providing a soft composite
actuator of claim 1 or 25; and pressurizing the bladder with a
fluid, wherein the soft composite actuator actuates in a
predetermined manner.
38. The method of claim 37, wherein actuation of the soft composite
actuator achieves one or more motions selected from the group
consisting of bending motion, combination bending, twisting motion,
linear extension, a combination of linear extension and twist,
linear contraction, a combination of linear contraction and twist,
and any combination thereof.
39. The method of claim 37, wherein the soft composite actuator is
configured to open an incision or move, displace organs, muscle,
and/or bone, brace a joint, be worn to support joint movements,
shape-match an object, fold pre-defined bending joints to create
origami-like structures, achieve a sufficient grasp over the
object, create a padded layer conformal to the object, distribute
forces, mix material, hand material, lift object, grasp object,
steer a photovoltaic cell or a mirror, or steer material on a
surface.
40. The method of claim 37, wherein the pressurized fluid is
temperature-regulated.
41. The method of claim 37, wherein the soft composite actuator
stiffens upon fluid pressurization.
42. The method of claim 37, wherein the bladder is configured to be
inflated to a first degree of stiffness under a first fluid
pressure or to a second degree of stiffness under a second fluid
pressure different from the first fluid pressure.
Description
INCORPORATION BY REFERENCE
All patents, patent applications and publications cited herein are
hereby incorporated by reference in their entirety in order to more
fully describe the state of the art as known to those skilled
therein as of the date of the invention described herein.
BACKGROUND
Most robots are constructed using so-called "hard" body plans; that
is, a rigid (usually metal) skeleton, electrical or hydraulic
actuation, electromechanical control, sensing, and feedback. These
robots are successful at the tasks for which they were designed
(e.g., heavy manufacturing in controlled environments) but have
severe limitations when faced with more demanding tasks (for
example, stable motility in demanding environments): tracks and
wheels perform not as efficiently as legs and hooves.
Evolution has selected a wide range of body plans for mobile
organisms. Many approaches to robots that resemble animals with
skeletons are being actively developed: "Big Dog" is an example. A
second class of robot--those based on animals without
skeletons--are much less explored, for a number of reasons: i)
there is a supposition that "marine-like" organisms (squid) will
not operate without the buoyant support of water; ii) the materials
and components necessary to make these systems are not available;
iii) the major types of actuation used in them (for example,
hydrostats) are virtually unused in conventional robotics. These
systems are intrinsically very different in their capabilities and
potential uses than hard-bodied systems. While they will (at least
early in their development) be slower than hard-bodied systems,
they will also be more stable and better able to move through
constrained spaces (cracks, rubble), lighter, and less
expensive.
Robots, or robotic actuators, which can be described as "soft" are
most easily classified by the materials used in their manufacture
and their methods of actuation. Pneumatic soft robotic actuators
can be manufactured using inextensible materials, which rely on
architectures such as follows. McKibben actuators, also known as
pneumatic artificial muscles (PMAs), rely on the inflation of a
bladder constrained within a woven sheath which is inextensible in
the axis of actuation. The resultant deformation leads to radial
expansion and axial contraction; the force that can be applied is
proportional to the applied pressure. Related actuators are called
pleated pneumatic artificial muscles.
There are "soft" robotic actuators such as shape memory alloys
which have been used both as the actuation method and as the main
structural component in robots which can both crawl and jump.
Another approach, which can be described as "soft" uses a
combination of traditional robotic elements (an electric motor) and
soft polymeric linkages based on Shape Deposition Manufacturing
(SDM). This technique is a combination of 3D printing and milling.
An example of a composite of traditional robotics with soft
elements has been used with success in developing robotic grippers
comprising soft fingers to improve the speed and efficiency of soft
fruit packing in New Zealand.
Soft robotics using interconnected channels in a molded elastomeric
have been reported. Soft robotics can be actuated using pneumatic
pressure to cause the robot to undergo a range of motions. The
basic soft robotic actuator includes an extensible channel or
bladder that expands against a stiffer or less extensible backing.
See, PCT Appln. Ser. No. PCT/US11/61720 for additional information
on the design and actuation of soft robotics, the contents of which
are incorporated in its entirety by reference.
Molding is one way to make soft robotic actuators; however, it is a
batch process. There thus remains a need for low cost, simple, and
high throughput methods for making soft robotics. There also
remains a need for new, simple, and efficient designs for soft
robotic actuation devices.
SUMMARY
Described herein are soft composite actuators which can be produced
easily and efficiently. The soft composite actuator as disclosed
herein can be manufactured by bonding two or more material layers
or sheets together. The material layers may be bonded together to
form one or more bladder configured to hold pressurized fluid. The
soft composite actuator may be actuated when the bladder therein is
pressurized by infusing fluids into the bladder. The bonding may be
achieved by mechanical, thermal, and/or chemical means or
combination thereof. The soft composite actuator as disclosed
herein can be manufactured without using any mold.
In some embodiments, one of the material layers is made of a
thermoplastic elastomer material which can be thermally bonded (or
high frequency welded or ultrasonically welded) together with other
layers to define the actuator's bladder (e.g., air tight bladders).
These constructions could also be achieved with chemical and
mechanical bonds or a combination thereof. Methods of making and
using the soft composite actuator are also disclosed herein.
In one aspect, a soft composite actuator is described, including: a
strain limiting layer; a first radially constraining layer; and a
first elastomeric layer disposed between the first radially
constraining layer and the strain limiting layer; wherein the first
elastomeric layer, the strain limiting layer, and the first
radially constraining layer are bonded together to form at least
one bladder for holding pressurized fluid.
In any embodiment described herein, the bond is selected from the
group of thermal bonds, chemical bonds, mechanical bonds and
combinations thereof.
In any embodiment described herein, the soft composite actuator
further includes a second elastomeric layer disposed adjacent to
the first elastomeric layer and the strain limiting layer comprises
a second radially constraining layer.
In any embodiment described herein, the radially constraining layer
includes one or more radially constraining sections.
In any embodiment described herein, the radially constraining
sections includes radially constraining strips evenly or unevenly
distributed in the radially constraining layer.
In any embodiment described herein, the radially constraining
strips are oriented parallel to one of the edges of the radially
constraining layer or at an angle to one of the edges of the
radially constraining layer.
In any embodiment described herein, the radially constraining
strips are bonded to the first elastomeric layer.
In any embodiment described herein, the radially constraining layer
includes one or more strain limiting sections free from any
openings.
In any embodiment described herein, the radially constraining layer
includes: one or more openings through which one or more portions
of the adjacent first elastomeric layer expand upon actuation, and
one or more strain limiting sections free from any openings.
In any embodiment described herein, the first elastomeric layer,
the strain limiting layer, and the first radially constraining
layer are bonded together to form a plurality of bladders for
holding pressurized fluid.
In any embodiment described herein, the soft composite actuator
further includes one or more rigid elements attached to the strain
limiting layer.
In any embodiment described herein, the bladder is designed to
accommodate a pressurized fluid selected from the group consisting
of a gas and a liquid.
In any embodiment described herein, one of the elastomeric layer,
the strain limiting layer, and the radially constraining layer is
configured to absorb fluids, transmit light, change color or
luminescence, embed a soft sensor or a medical patch, embed at
least a part of an electronic circuit or a heating element, and a
combination thereof.
In any embodiment described herein, the soft composite actuator is
part of a splint, a grasper, or a glove comprising a plurality of
digits, or is a splint, a grasper, or a glove.
In another aspect, a soft composite actuator is described,
including: a monolithic, first composite layer including one or
more first elastomeric sections and one or more first radially
constraining sections; and a strain limiting layer, wherein the
first composite layer and the strain limiting layer are bonded
together to form at least one bladder for holding pressurized
fluid.
In any embodiment described herein, the strain limiting layer
includes a monolithic, second composite layer including one or more
second elastomeric sections and one or more second radially
constraining sections.
In any embodiment described herein, the first and/or second
elastomeric section, the first and/or second radially constraining
section, and the first and/or second composite layer have the same
thickness.
In any embodiment described herein, the first and/or second
elastomeric section and the first and/or second radially
constraining section have different thickness.
In any embodiment described herein, the first and/or second
radially constraining section is encapsulated in the first and/or
second elastomeric section.
In any embodiment described herein, the first and/or second
elastomeric sections and the first and/or second radially
constraining sections are bonded together.
In any embodiment described herein, the bond is selected from the
group of thermal bonds, chemical bonds, mechanical bonds and
combinations thereof.
In any embodiment described herein, the radially constraining
sections comprise radially constraining strips oriented parallel to
one of the edges of the composite layer or at an angle to one of
the edges of the composite layer.
In any embodiment described herein, the radially constraining
strips are evenly or unevenly distributed in the composite
layer.
In any embodiment described herein, the first composite layer and
the strain limiting layer are bonded together to form a plurality
of bladders for holding pressurized fluid.
In any embodiment described herein, the soft composite actuator
further includes one or more rigid elements attached to the strain
limiting layer.
In any embodiment described herein, the bladder is designed to
accommodate a pressurized fluid selected from the group consisting
of a gas and a liquid.
In any embodiment described herein, one of the layers is configured
to absorb fluids, transmit light, change color or luminescence,
embed a soft sensor or a medical patch, embed at least a part of an
electronic circuit or a heating element, and a combination
thereof.
In any embodiment described herein, the soft composite actuator is
part of a splint, a grasper, or a glove comprising a plurality of
digits, or is a splint, a grasper, or a glove.
In yet another aspect, a soft actuating device including a
plurality of the soft composite actuators of any one of embodiments
is described.
In any embodiment described herein, the soft actuating device
includes: a first soft composite actuator connected to a first
fluid source; and a second soft composite actuator connected to a
second fluid source.
In yet another aspect, a method of actuation is described,
including: providing a soft composite actuator of any one of
embodiments; and pressurizing the bladder with a fluid, wherein the
soft composite actuator actuates in a predetermined manner.
In any embodiment described herein, actuation of the soft composite
actuator achieves one or more motions selected from the group
consisting of bending motion, combination bending, twisting motion,
linear extension, a combination of linear extension and twist,
linear contraction, a combination of linear contraction and twist,
and any combination thereof.
In any embodiment described herein, the soft composite actuator is
configured to open an incision or move, displace organs, muscle,
and/or bone, brace a joint, be worn to support joint movements,
shape-match an object, fold pre-defined bending joints to create
origami-like structures, achieve a sufficient grasp over the
object, or create a padded layer conformal to the object.
In any embodiment described herein, the pressurized fluid is
temperature-regulated.
In any embodiment described herein, the soft composite actuator
stiffens upon fluid pressurization.
In any embodiment described herein, the bladder is configured to be
inflated to a first degree of stiffness under a first fluid
pressure or to a second degree of stiffness under a second fluid
pressure different from the first fluid pressure.
In any embodiment described herein, the actuator is actuated to
distribute forces, mixing material, handling material, lifting,
grasping, steering a photovoltaic cell or a mirror, steering
material on a surface.
In yet another aspect, a method of actuation is described,
including: providing the soft actuating device of any one of the
embodiments described herein; and pressurizing one or more bladders
with one or more fluids, wherein the soft actuating device actuates
in a predetermined manner.
In yet another aspect, a method of actuation is described,
including: providing the soft actuating device of any one of the
embodiments described herein; and pressurizing the first soft
composite actuator's bladder and the second soft composite
actuator's bladder alternately by activating the first fluid source
and the second fluid source alternately. the first soft composite
actuator bends upon actuation and the second soft composite
actuator stiffens upon actuation.
In yet another aspect, a method of making a soft composite actuator
of any one of the embodiments described herein is disclosed,
including: providing a first elastomeric layer, a strain limiting
layer, and a first radially constraining layer; wherein the
elastomeric layer is disposed between the radially constraining
layer and the strain limiting layer; and bonding the first
elastomeric layer, the strain limiting layer, and the first
radially constraining layer to form sealed parameters defining at
least one bladder for holding pressurized fluid.
In any embodiment described herein, providing a first elastomeric
layer, a strain limiting layer, and a first radially constraining
layer includes: providing a pre-stacked laminate comprising a first
elastomeric laminate layer, a strain limiting laminate layer, and a
first radially constraining laminate layer; and separating part of
the laminate to provide the first elastomeric layer, the strain
limiting layer, and the first radially constraining layer stacked
together.
In yet another aspect, a method of making a soft composite actuator
of any one of the embodiments described herein is disclosed,
including: providing the first composite layer and the strain
limiting layer; and bonding the first composite layer and the
strain limiting layer to form sealed parameters defining at least
one bladder for holding pressurized fluid.
In any embodiment described herein, providing the first composite
layer and the strain limiting layer including: providing a
pre-stacked laminate comprising a first composite laminate layer
and a strain limiting laminate layer; and separating part of the
laminate to provide the first composite layer and the strain
limiting layer stacked together.
In any embodiment described herein, the bond is selected from the
group of thermal bonds, chemical bonds, mechanical bonds and
combinations thereof.
In any embodiment described herein, the elastomeric layer, the
strain limiting layer, and the radially constraining layer are
contained in a package.
In any embodiment described herein, bonding is achieved by external
heat passing through the packaging or internal heat generated by a
heating element inside the packaging without the compromise of the
package.
In any embodiment described herein, the elastomeric layer or the
first composite layer is in a pre-strained state before
bonding.
In any embodiment described herein, one of the layers has a
non-planar shape before or during bonding.
The combination of any one embodiment described herein with any
other one or more embodiments described herein is contemplated.
Unless otherwise defined, used or characterized herein, terms that
are used herein (including technical and scientific terms) are to
be interpreted as having a meaning that is consistent with their
accepted meaning in the context of the relevant art and are not to
be interpreted in an idealized or overly formal sense unless
expressly so defined herein. For example, if a particular
composition is referenced, the composition may be substantially,
though not perfectly pure, as practical and imperfect realities may
apply; e.g., the potential presence of at least trace impurities
(e.g., at less than 1 or 2%) can be understood as being within the
scope of the description; likewise, if a particular shape is
referenced, the shape is intended to include imperfect variations
from ideal shapes, e.g., due to manufacturing tolerances.
Percentages or concentrations expressed herein can represent either
by weight or by volume.
Although the terms, first, second, third, etc., may be used herein
to describe various elements, these elements are not to be limited
by these terms. These terms are simply used to distinguish one
element from another. Thus, a first element, discussed below, could
be termed a second element without departing from the teachings of
the exemplary embodiments. Spatially relative terms, such as
"above," "below," "left," "right," "in front," "behind," and the
like, may be used herein for ease of description to describe the
relationship of one element to another element, as illustrated in
the figures. It will be understood that the spatially relative
terms, as well as the illustrated configurations, are intended to
encompass different orientations of the apparatus in use or
operation in addition to the orientations described herein and
depicted in the figures. For example, if the apparatus in the
figures is turned over, elements described as "below" or "beneath"
other elements or features would then be oriented "above" the other
elements or features. Thus, the exemplary term, "above," may
encompass both an orientation of above and below. The apparatus may
be otherwise oriented (e.g., rotated 90 degrees or at other
orientations) and the spatially relative descriptors used herein
interpreted accordingly. Further still, in this disclosure, when an
element is referred to as being "on," "connected to," "coupled to,"
"in contact with," etc., another element, it may be directly on,
connected to, coupled to, or in contact with the other element or
intervening elements may be present unless otherwise specified.
The terminology used herein is for the purpose of describing
particular embodiments and is not intended to be limiting of
exemplary embodiments. As used herein, singular forms, such as "a"
and "an," are intended to include the plural forms as well, unless
the context indicates otherwise. Additionally, the terms,
"includes," "including," "comprises" and "comprising," specify the
presence of the stated elements or steps but do not preclude the
presence or addition of one or more other elements or steps. The
term "laminate" and "soft composite actuator" may be used
interchangeably.
DESCRIPTION OF THE DRAWINGS
The invention is described with reference to the following figures,
which are presented for the purpose of illustration only and are
not intended to be limiting. In the Drawings:
FIG. 1A presents an exploded and assembled view of an actuatable
device capable of bending that includes two layers bonded together
such that the bond defines an airtight (or water tight) bladder:
one layer having strain limiting properties and the other layer
having elastic properties, according to one or more embodiments
described herein.
FIG. 1B presents a perspective view of the two-layer bending
actuator under fluid pressurization where the elastic layer swells
and grows in radius and in length, according to one or more
embodiments described herein.
FIG. 1C is a perspective view of the two-layer bending actuator
under fluid pressurization where at a certain pressure the swelling
elastic layer will cause the strain limited layer to bend,
according to one or more embodiments described herein.
FIG. 2A is an exploded and assembled view of an actuatable device
capable of bending that includes three layers bonded together such
that the bond defines an airtight (or water tight) bladder,
including: one layer having radial strain limited properties, one
layer having elastic properties, and another layer having strain
limiting properties, according to one or more embodiments described
herein.
FIG. 2B is a side view of the three-layer bending actuator
according to one or more embodiments described herein under fluid
pressurization where the radially constraining layer limits radial
expansion of the elastic layer and promotes linear growth by
allowing the elastic layer to expand via the cut outs of the
radially constraining layer.
FIGS. 2C-G describe a process where two radially constraining
layers and two elastic layers can be bonded to form a linear
extending actuator, according to one or more embodiments described
herein.
FIG. 2C presents an exploded view of the layer assembly, according
to one or more embodiments described herein.
FIG. 2D depicts half of the assembly where after bonding, the
excess material from the radially constraining layer can be removed
leaving strain limiting strips bonded to the elastic layer,
according to one or more embodiments described herein.
FIG. 2E is a cross-section view of the laminate without and with
fluid pressurization, according to one or more embodiments
described herein.
FIG. 2F is a perspective view of the linear extending actuator in
an unpressurized state, according to one or more embodiments
described herein.
FIG. 2G is a perspective view of the linear actuator according to
one or more embodiments described herein extending under fluid
pressurization where the strain limiting strips, connected by the
bond, form radially constraining hoops along the length of the
actuator, thus promoting linear extension.
FIG. 2H demonstrates that changing the orientation of the strain
limiting strips to the longest dimension of the actuator can be
used as an approach to make a contracting linear actuator (i.e.,
the largest deformation is contractile), according to one or more
embodiments described herein.
FIG. 3A presents an exploded view of a bending actuatable device
including layers preformed to a particular shape before or during
assembly so that the actuator takes on a non-planar profile in its
unpressurized state, according to one or more embodiments described
herein.
FIG. 3B presents a perspective view of the assembled bending
actuator in its unpressurized state, according to one or more
embodiments described herein.
FIG. 3C presents a side view of the bending actuator in a
pressurized state, according to one or more embodiments described
herein.
FIG. 4A presents an exploded and assembled view of a bending
actuatable device including two layers, where one layer has
anisotropic properties such that it prefers to stretch along the
y-axis and is strain-limited along the x-axis and the other layer
is strain limited in both the x and y direction, according to one
or more embodiments described herein.
FIG. 4B presents a side view of the two-layer bending actuator
under fluid pressurization, wherein the anisotropic layer performs
a dual function of promoting linear growth while limiting radial
expansion to cause the assembly to bend, according to one or more
embodiments described herein.
FIG. 4C is a perspective view of an assembled linear-extending
actuator including two anisotropic layers bonded together to form
an airtight (or water tight) bladder, according to one or more
embodiments described herein.
FIG. 4D is a side view of the linear-extending actuator under fluid
pressurization where the strain limiting portions of the
anisotropic layer form hoops that limit radial expansion and
promote linear extension, according to one or more embodiments
described herein.
FIG. 4E is an exploded and assembled view of an actuatable device
capable of bending and twisting under fluid pressurization,
according to one or more embodiments described herein.
FIG. 4F is an exploded and assembled view of an actuatable device
capable of linear extension and twisting under fluid pressurization
by bonding two anisotropic layers with angled elastic and strain
limiting elements, according to one or more embodiments described
herein.
FIG. 5A shows the profile of a radially constraining layer (top)
and the response of the actuator (bottom) under fluid
pressurization, according to one or more embodiments described
herein.
FIG. 5B is an extension of FIG. 5A demonstrating that several
joints can be designed into a single actuator to form a closed
shape, according to one or more embodiments described herein.
FIG. 5C is an extension of FIG. 5A, demonstrating that multiple
bending actuators can be combined on a single laminate, according
to one or more embodiments described herein.
FIG. 6A depicts a top view and an isometric view of an actuatable
device that combines a multiple functions onto a single laminate,
where two bending actuators are connected via two stiffeners,
according to one or more embodiments described herein.
FIG. 6B is an extension of FIG. 6A where multiple stiffeners can be
used to support bending actuators and achieve greater coverage,
according to one or more embodiments described herein.
FIG. 7A depicts an exploded view and cross-section view of an
actuatable device that incorporates rigid elements as an additional
layer that can be used to define bending points, adjust the bending
radius of curvature, improve force transmission, and act as a
mounting substrate for auxiliary equipment, according to one or
more embodiments described herein.
FIG. 7B is a side view of a bending actuator under fluid
pressurization with rigid elements where it only bends at the gaps
between the rigid elements, according to one or more embodiments
described herein.
FIG. 8A is an exploded view of a bimorph bending actuator that
consists of a single bending actuator and incorporates a
pre-strained layer during the assembly, according to one or more
embodiments described herein.
FIG. 8B shows the range of motion of the bimorph bending actuator
at different stages of pressurization, according to one or more
embodiments described herein.
FIG. 8C illustrates that opposing bimorph bending actuators can be
used to form a grasper, according to one or more embodiments
described herein.
FIG. 9A is an extension of FIG. 4C where multiple linear extending
actuators can be grouped on the same laminate to form a
multi-degree of freedom bending and extending actuator, according
to one or more embodiments described herein.
FIG. 9B is an end view of FIG. 9A and depicts the next stage in the
fabrication of a multi-degree of freedom bending and extending
actuator where the laminate is bonded end to end to form a tube
shape, according to one or more embodiments described herein.
FIG. 9C illustrates that when one bladder is pressurized it will
linearly extend causing the tube structure to bend, according to
one or more embodiments described herein.
FIG. 10 is a perspective view of a wearable application where soft
actuators have been incorporated into a glove to assist joint
motions, according to one or more embodiments described herein.
FIG. 11 is perspective view of a material layer demonstrating
multi-functionality and optionally incorporating electronics,
heating elements, sensors, and so forth, according to one or more
embodiments described herein.
FIG. 12 shows a sequence of side views of an actuatable device that
uses connected pressurized bladders to transmit force, according to
one or more embodiments described herein.
FIG. 13A shows a sequence of images where a rolled sheet of
actuatable devices can be cut to a desired length and the bladders
can be resealed with a sealing tool, according to one or more
embodiments described herein.
FIG. 13B illustrates how these sheets of actuatable devices can be
sealed and bonded together to form a range of different actuatable
structures, according to one or more embodiments described
herein.
FIG. 14 depicts a process by which the bladders of actuatable
devices can be defined while the layers of the laminate are
contained within packaging (both sterile and non-sterile),
according to one or more embodiments described herein.
DETAILED DESCRIPTION
Described herein are soft composite actuators made by bonding two
or more material layers. A material layer, as used herein, may
refer to an elastomeric layer, a strain limiting layer, a radially
constraining layer, or a first or second composite layer including
one or more elastomeric sections and one or more radially
constraining sections. The elastomeric layer, as used herein,
refers to a layer which is made of one or more elastic materials
and can be bent, curved, twisted, or subjected to any other motion
to change its shape and/or orientation under pressure. Non-limiting
examples of the elastic material include elastic polymer (e.g.
urethanes and silicones), thermoplastic elastomers (TPEs),
thermoplastic urethanes (TPUs) and so forth. As used herein,
"elastomeric" and "elastic" are used interchangeably.
In some embodiments, the material layer is a strain limiting layer.
The strain limiting layer, as used herein, refers to any layer
which is not elastic or less elastic than the elastomeric layer. As
a result, under actuation (e.g., pressurization of the bladder),
the changes in the shape or orientation of the elastomeric layer,
not that of the strain limiting layer, will predominantly determine
the shape, curvature, and/or orientation of the soft composite
actuator after actuation. In some embodiments, the strain limiting
layer is made of one or more strain limiting materials.
Non-limiting examples of the strain limiting material include
fibers, thread, non-woven materials, and higher duromoter materials
to name a few. Any other materials known in the art suitable as the
strain limiting material can be used.
In other embodiments, the material layer is a radially constraining
layer which limits the radial expansion of the resulting bladder
and promotes efficient bending. In some specific embodiments, the
radially constraining layer can have strain limiting properties
such as those of the strain limiting layer. The radially
constraining layer employs the strain limiting material to restrict
the radial expansion of the bladder in the soft composite actuator.
In one or more embodiments, the radially constraining layer is a
sheet of high durometer material that contains openings, e.g.,
cutouts, which provide radially constraining regions (e.g., strips
or bands) of spaced at locations to allow portions of the adjacent
elastomeric layer to expand through the cutouts. The radially
constraining regions are positioned and arranged (e.g., as bands or
stripes traversing the width of the soft composite actuators) so
that the elastomeric layer's radial expansion will be limited or
restricted. In some embodiments, the radially constraining regions
are evenly or unevenly distributed in the radially constraining
layer. In some specific embodiments, the radially constraining
regions, e.g., strips 220 in FIG. 2C, are oriented parallel to one
of the edges of the radially constraining layer or at an angle to
one of the edges of the radially constraining layer. The angle
(.theta.) can be in any ranges or have any values. In some
embodiments, .theta. is about 10, 20, 30, 40, 45, 50, 60, 70, 80
degree, or in any ranges bound by any two of the values disclosed
herein.
In some specific embodiments, the radially constraining layer or
section restrict the radial swelling of the bladder or elastomeric
layer to promote more efficient bending of the actuator by
supporting linear extension of the elastic layer and limiting
radial expansion, which does not promote bending. In still other
embodiments, the radially constraining region can be incorporated
into a layer containing other materials. By way of example, the
radially constraining layer or strain limiting layer can be a
monolithic composite layer, e.g., layer 401 in FIG. 4A, comprising
one or more elastomeric sections and one or more radially
constraining sections. The elastomeric section may be made of
elastomeric materials and the radially constraining section may be
made of strain limiting materials.
In certain embodiments, the radially constraining layer comprises
one or more individual radially constraining sections, which can be
assembled and bonded to form a radially constraining layer. In
certain specific embodiments, the radially constraining sections
comprise radially constraining strips evenly or unevenly
distributed in the radially constraining layer. The radially
constraining strips, e.g., strips 405 in FIG. 4A, may be oriented
parallel to one of the edges of the radially constraining layer or
at an angle to one of the edges of the radially constraining layer.
The angle (.theta.) can be in any ranges or have any values. In
some embodiments, .theta. is about 10, 20, 30, 40, 45, 50, 60, 70,
80 degree, or in any ranges bound by any two of the values
disclosed herein. The radially constraining strips may be bonded to
the first elastomeric layer.
In some embodiments, the material layer is a radially constraining
layer described above.
The two or more material layers are bonded together to form sealed
at least one bladder for holding pressurized fluid. In some
embodiments, the perimeters or certain portions of two adjacent
material layers in the soft composite actuator are bonded together
to result in a fluid-tight bladder, except that the bladder may be
connected to a fluid infusion/vacuum source. In certain
embodiments, the perimeters or certain portions of the adjacent
elastomeric layer and the strain limiting layer in the soft
composite actuator are bonded together to result in a fluid-tight
bladder. In other embodiments, the perimeters or certain portions
of the adjacent first composite layer and the strain limiting layer
in the soft composite actuator are bonded together to result in a
fluid-tight bladder. In still other embodiments, the perimeters or
certain portions of the adjacent first composite layer and the
second composite layer in the soft composite actuator are bonded
together to result in a fluid-tight bladder. In still other
embodiments, the soft composite actuator comprises two elastomeric
layers and the perimeters or certain portions of the two adjacent
elastomeric layers are bonded together to result in a fluid-tight
bladder.
In other embodiments, the radially constraining layer comprises one
or more strain limiting sections free from any openings. Thus, the
radially constraining layer may include one or more openings
through which one or more portions of the adjacent first
elastomeric layer expand upon actuation, and one or more strain
limiting sections free from any openings. Upon actuation, such soft
composite actuator may bend at the portion of the radially
constraining layer having the openings and may stiffen at the
portion of the radially constraining layer free from any
openings.
In some embodiments, the bladder is airtight except its connection
to an external fluid source to infuse pressurized fluid into the
bladder. Non-limiting examples of the fluids include a gas and a
liquid. Non-limiting examples of the fluid source include a gas
tank, a gas cylinder, a liquid pump, compressor, gases given off by
a chemical reaction, and so forth. The gas may be air, nitrogen, or
one of the inert gases. The liquid may include water, aqueous
solution, and organic solvents or solutions. Upon actuation (e.g.,
when the bladder is infused with pressurized fluid), the soft
composite actuator may actuate in a pre-determined way to change
the actuator's shape, size, orientation, and/or curvature, to
achieve one or more desirable functions. The soft actuator may have
one bladder or a plurality of bladders connected to the same or
different fluid sources.
In one aspect, a soft composite actuator is described, including
comprising: an elastomeric layer; a strain limiting layer; and a
radially constraining layer, wherein the elastomeric layer is
disposed between the radially constraining layer and the strain
limiting layer; and the elastomeric layer, the strain limiting
layer, and the radially constraining layer are bonded together to
form at least one bladder for holding pressurized fluid.
The strain limiting layer may be located at the top or bottom of
the soft composite actuator. The layered soft composite actuator
allows for the control of the direction of expansion. For instance,
FIGS. 1-3 show that the soft composite actuator can be constructed
by layering materials of different elasticity and subtracting
material (e.g., elastomeric layer, strain limiting layer, and
radially constraining layer).
The actuation mechanism of the soft composite actuator is first
described with reference to FIGS. 1A-1C. As shown in FIG. 1A, an
elastic layer 101 and a strain limiting layer 103 are bonded at the
layers' perimeter 105. The bonding may be achieved thermally,
mechanically, and/or chemically. In some embodiments, the elastic
layer is made of elastic polymers which can be thermally bonded to
other layers such as the strain limiting layer. The term "elastic
layer" or "elastic section" (described below), as used herein,
refers to any material layer or section made of material having
elastic properties and can bend or expand under pressure. The term
"strain limiting layer", as used herein, refers to any material
layer which is not elastic or less elastic than the elastic
material forming the elastic layer or the elastic section in the
composite layer described below. The bonding of the elastic layer
101 and the strain limiting layer 103 results in the formation of
an airtight bladder 107, which is sealed off except its connections
to an outside fluid infusion/vacuum source configured to inflate or
deflate the bladder by infusing and removing the fluid in and out
of the bladder.
Thus, when two different material layers (i.e., one elastic layer
101 and one strain limiting layer 103) are bonded to form a
bladder, the resulting structure 109 has an anisotropic response to
pressurized fluid in the bladder. The elastic layer 101 expands
while the strain limiting layer 103 undergoes limited expansion.
The difference in strain responses between the two layers may cause
the structure to bend in the direction of the strain limited layer
(FIG. 1C). FIG. 1B illustrates the soft composite actuator with a
bladder 111 partially filled by pressured fluid from the fluid
infusion/vacuum source 115. The partially filled bladder has an
inside pressure higher than the outside pressure (Op) so that the
elastic layer 113 is curved. When the bladder is fully filled by
the pressured fluid, the linear growth of the portion of the
elastic layer forming the inflated air tight bladder (portion 117
in FIG. 1C) will eventually cause the strain limited layer 119 to
bend. The circumferential constraint, i.e., the bonding at the
perimeter 105, is beneficial because without such circumferential
constraints, the material layer has considerable radial growth
which after a certain point (e.g., when the material approaches its
yield stress or fatigue yield stress), is not useful for the
purposes of the bending.
A soft composite actuator according to one or more embodiments is
described with reference to FIGS. 2A-2H. As shown in FIG. 2A, an
elastomeric layer 203 is disposed between a radial constraining
layer 201 and a strain limiting layer 205. The perimeters of layers
201, 203, and 205, e.g., portion 207 are bonded together thermally
to result in soft composite actuator 209, which upon actuation
bends in a predetermined fashion (FIG. 2B). The bonding may also be
achieved by chemical method, mechanical method, and a combination
thereof. One of the advantages of the instant application is that
the soft composite actuator described herein can be made without
using any mold, thus the manufacture process is greatly simplified.
In some embodiments, heat can be applied to two or more material
layers, e.g., elastomeric layer and strain limiting layer, to bond
the layers together. In other embodiments, mechanical force by hand
or machine can be applied to two or more material layers, e.g.,
elastomeric layer and strain limiting layer, to bond the layers
together. In still other embodiments, chemical reactants can be
deposited between the material layers or embedded in one or more
material layers and a chemical reaction may be initiated to bond
the two or more material layers, e.g., elastomeric layer and strain
limiting layer, together.
As shown in FIG. 2B, the soft composite actuator 209 contains a
bladder formed by the bonding of the perimeters of layers 201 and
203. This bladder (213 in FIG. 2B) is connected to an
infusion/vacuum source 211 to infuse pressurized liquid into
bladder 213. The fluid-filled bladder has an inside pressure higher
than the outside pressure (Op) which forces the elastomeric layer
203 and the radially constraining layer 201 to bend towards the
strain limiting layer 205.
Thus, as shown in FIGS. 2A-2C, an additional layer, i.e., the
radially constraining layer, can be added to create an additional
anisotropic response by limiting the radial expansion of the
elastic layer. The cutouts (215) on the radially constraining layer
allow the elastic layer to expand lengthwise while limiting strain
limiting regions or bands 216 limit radial expansion. Restricting
the radial swelling of the bladder promotes more efficient bending
by supporting linear extension of the elastic layer and limiting
radial expansion, which does not promote bending. It should be
noted that additional layers could be added to include other
functionalities such as super absorbent material to soak up fluids,
antibacterial properties, hot therapy, and cold therapy.
The soft composite actuator can be designed and configured to
actuate in a predetermined manner upon pressurization of the
bladder and/or perform one or more desirable functions. Upon
actuation, the soft composite actuator may be designed to generate
structural anisotropy or structural isotropy. That is, the soft
composite actuator may upon actuation generate the same or
different structural changes when measured along different axes of
the soft composite actuator.
In some embodiments, the soft composite actuator further includes a
second elastomeric layer, and a bladder can be formed by, for
example, thermally sealing the edges of the two elastomeric layers.
In some embodiments, the strain limiting layer in the soft
composite actuator is also a radially constraining layer which
limits the radial expansion of the elastomeric layer. These designs
are described with reference to FIGS. 2C-2G, which show a linear
extending actuator including two radially constraining layers and
two elastic layers bonded to form a linear extending actuator.
As shown in FIG. 2C, a first and second elastomeric layers, 223 and
225, respectively, are sandwiched between a first radially
constraining layer 217 and a strain limiting layer (i.e., a second
radially constraining layer 221). The radially constraining layers
217 and 221 contain cutouts 219 and 227, respectively. After layers
217, 223, 225, and 221 are bonded at their perimeters, e.g., edge
229, to form composite 231, some portions of the soft composite
actuator, e.g., portions 235 and 237, can be cut off along the
dotted lines shown in FIG. 2D to form soft composite actuator 233.
These excess materials from the radially constraining layers 217
and 221 are removed leaving strain limiting strips 243 bonded to
the elastic layers. FIG. 2E is a cross-section view of the soft
composite actuator 233 without (upper portion of FIG. 2E) and with
fluid pressurization (lower portion of FIG. 2E). As shown in FIG.
2E, the soft composite actuator has layers 217, 221, 223, and 225
bonded together at the edge 229. Upon actuation, bladder 239
between layers 223 and 225 is pressurized to generate an inside
pressure of P.sub.1, which is greater than the outside pressure
P.sub.atm. As a result, the layers of the actuator 233 curve as
shown in the lower portion of FIG. 2E.
FIG. 2F is a perspective view of the linear extending actuator 233
in an unpressurized state. Edges of the layers, e.g., 241 and 247,
are bonded (FIG. 2G). FIG. 2G is a perspective view of the linear
actuator 233 in the actuated state extending under fluid
pressurization where the strain limiting strips 243 in the radially
constraining layer 217, connected by the bond at edge 241, form
radially constraining hoops along the length of the actuator, and
thus promote linear extension along the direction of axis 245.
FIG. 2H demonstrates that when the orientation of the strain
limiting strips 251 run length wise, i.e., along axis 253, the
resulting soft composite actuator is a contracting linear actuator
249, (i.e. the largest deformation is contractile). FIG. 2H shows
the contracting linear actuator 249 in its unactuated state (upper
left corner of FIG. 2H) and actuated state (lower right corner of
FIG. 2H).
In certain embodiments, the pressurized fluid is
temperature-regulated to deliver hot or cold therapy. For instance,
fluidic lines could also be heat stamped into a material layer for
delivery hot and/or cold therapy or even medicine.
As shown in FIGS. 2A-2H, the elastomeric layer, the strain limiting
layer, and the radially constraining layer may have a planar shape
before or during bonding. In some other embodiments, at least of
the elastomeric layer, the strain limiting layer, and the radially
constraining layer may have a non-planar shape before or during
bonding.
In one or more embodiments, one or more layers of the soft
composite actuator can be preformed into a non-planar shape before
assembly. FIG. 3A is an exploded view of a bending soft composite
actuator including layers that are preformed to a particular shape
before or during assembly so that the actuator takes on a
non-planar profile in its unpressurized state. The soft composite
actuator includes the pre-formed radially constraining layer 301, a
pre-formed elastic layer 303, and a strain limiting layer 305.
These material layers are bonded at the perimeters of the material
layers, e.g., perimeter 307 to form a bending soft composite
actuator 309 (FIG. 3B). The bladder formed in the actuator 309 is
connected to a pressurized fluid source via a tube 311. Other types
of connection known in the art are contemplated. FIG. 3B is a
perspective view of the assembled bending actuator 309 in its
unpressurized state. FIG. 3C is a side view of the bending actuator
in a pressurized state. When the actuator 309 is actuated by
infusion of pressurized fluid through tube connection 311, radially
constraining layer 301 restricts the radial expansion of the
elastic layer 303 and actuator 309 bends in a predetermined matter,
i.e., towards the direction of strain limiting layer 305.
Thus, in some embodiments, it may be advantageous to pre-form
(e.g., thermally form) one or more material layers, e.g., radially
constraining layer, first and second composite layers (also
referred to anisotropic layer in FIGS. 4A-F), elastic layer, or
strain limiting layer, before or during actuator assembly so that
an actuator can be designed to achieve a particular thickness (or
pressurized profile) under fluid pressurization. In some
embodiments, preforming one or more materials is desirable for a
soft composite actuator to achieve desired range of motion,
stiffness, and force production as these outputs are linked to
actuator thickness. Pre-forming to a non-planar initial state may
also place less strain on the material to reach a target state,
which in turn, may reduce the required input pressure and material
fatigue. Non-limiting examples of the non-planar shapes of the
material layers include half cylinder shape (FIGS. 3A-3C),
rectangular, tapered, and bellows-shaped. Any material layer of any
of the soft composite actuator may be pre-formed.
In another aspect, a soft composite actuator is described,
including: a monolithic, first composite layer comprising one or
more first elastomeric sections and one or more first radially
constraining sections; and a strain limiting layer, wherein the
first composite layer and the strain limiting layer are bonded
together to form at least one bladder for holding pressurized
fluid.
The first composite layer is located at the top or bottom of the
soft composite actuator. In some embodiments, the first elastomeric
section, the first radially constraining section, and/or the first
composite layer have the same thickness. In these embodiments, the
first composite layer can be made by from bonding the first
elastomeric sections and the first radially constraining sections
together. In other embodiments, the first elastomeric section and
the first radially constraining section have different thickness.
In these embodiments, the first composite layer and the first
elastomeric section may have the same thickness. In some specific
embodiments, the first elastomeric section is thicker than the
first elastomeric section and/or the first elastomeric section
encapsulates the first radially constraining section.
The soft composite actuator according to this aspect is described
with reference to FIGS. 4A-4F. FIG. 4A is an exploded and assembled
view of a soft composite actuator 403 capable of bending and
including a first composite layer 401. The first composite layer
401 has radially constraining sections 405 made of strain limiting
materials and elastomeric section 407 made of elastic materials.
Sections 405 and 407 can be in any shape or size and are bonded
together by thermal, chemical, and/or mechanical methods to form
the monolithic first composite layer 401. Because the first
composite layer 401 has different expansion properties or
characteristics along the x and y axes (i.e., layer 401 may expand
more easily along the y axis than alone the x axis), the first
composite layer 401 is also referred to as a monolithic anisotropic
layer. As shown in FIG. 4A, sections 405 and 407 both have the same
thickness as that of the monolithic layer. The first composite
layer is then bonded with a strain limiting layer 409 to form the
bending soft composite actuator 403.
Thus, in the embodiments described in FIG. 4A, the first composite
layer 401 has anisotropic properties such that it prefers to
stretch along the y-axis and is strain-limited along the x-axis.
The strain limiting layer 409 is made of strain limiting material
and strain-limited is both the x and y directions. The layers are
bonded together at the two layers' perimeters such that the bond
defines a fluid tight (e.g., airtight or water tight) bladder.
FIG. 4B is a side view of the bending soft composite actuator 403
upon actuation when the bladder 411 is under fluid pressurization.
The anisotropic layer 401 performs a dual function of promoting
linear growth of the elastic sections 407 while limiting its radial
expansion to cause the assembly to bend.
In some embodiments, the strain limiting layer includes or is a
second composite layer comprising one or more second elastomeric
sections and one or more second radially constraining sections,
wherein the second elastomeric section, the second radially
constraining section, and the second composite layer have the same
or different thickness, wherein the second composite layer is a
monolithic anisotropic layer. Similar to the first composite layer,
the second elastomeric section and the second radially constraining
section can be bonded together to form the second composite layer.
Alternatively, the second radially constraining section may be
encapsulated in the second elastomeric section. The radially
constraining sections may be evenly or unevenly distributed in the
composite layer. In some embodiments, the radially constraining
sections comprise radially constraining strips oriented parallel to
one of the edges of the composite layer or at an angle to one of
the edges of the composite layer. The angle (.theta.) can be in any
ranges or have any values. In some embodiments, .theta. is about
10, 20, 30, 40, 45, 50, 60, 70, 80 degree, or in any ranges bound
by any two of the values disclosed herein. The soft composite
actuator according to these embodiments is described with reference
to FIGS. 4C-4D.
FIG. 4C is a perspective view of an assembled linear extending soft
composite actuator 413 which consists of two anisotropic layers 415
and 417 bonded together to form an airtight (or water tight)
bladder. The first composite layer 415 contains radially
constraining sections 421 made of strain limiting materials and
elastomeric section 419 made of elastic materials. Sections 419 and
421 are bonded together by thermal, chemical, and/or mechanical
methods to form the monolithic first composite layer. Sections 419
and 421 both have thickness the same as that of the first composite
layer 415.
The strain limiting layer 417 in FIG. 4C is also a second composite
layer containing radially constraining sections 425 made of strain
limiting materials and elastomeric section 423 made of elastic
materials. Sections 423 and 425 are bonded together by thermal,
chemical, and/or mechanical methods to form the monolithic first
composite layer. Sections 423 and 425 both have thickness the same
as that of the first composite layer 417.
Both layers 415 and 417 are anisotropic layers. FIG. 4D is a side
view of the linear extending actuator 413 before actuation (top
portion of FIG. 4D) and under fluid pressurization (lower portion
of FIG. 4D) where the strain limiting sections (421 and 425) of the
anisotropic layers 415 and 417 form hoops that limit radial
expansion and promote linear extension. As shown in FIG. 4D, upon
actuation the actuator extends a distance of .DELTA.L.
Thus, in these embodiments described above, the complexity of
bonding multiple material layers can be reduced by creating the
desired anisotropic properties into a single layer, e.g., the first
or second composite layer. The strain limiting sections (made of a
strain limited material such as fibers, thread, non-woven
materials, higher duromoter materials, etc.) can be combined with
the elastic sections to create a single, monolithic layer that is
more elastic in one direction (e.g., y-direction in FIG. 4A) over
another (e.g., x-direction in FIG. 4A). When this anisotropic layer
is bonded to the strain limited layer the result is a bending
actuator constructed from only two material layers. The anisotropy
contained in a single layer can be achieved several ways including
molding or encapsulating the strain limited material in the elastic
material, heat stamping the strain limited material together with
the elastomer, sandwiching two elastomer films around the strain
limited material, or cast extruding elastic and strain limiting
materials together. Furthermore, adjusting the spacing and
orientation of the elastic and strain limiting materials in the
anisotropic layer can enable the soft actuator to combine multiple
actuations in series such as stiffening sections, bending sections,
linear extending sections, linear extending and twisting, and
bend-twist sections (see, e.g., FIG. 5A for an example actuator
with stiff sections and bending sections). Similarly, the
anisotropic layer can be bonded with another anisotropic layer to
make a linear actuator (extending and contracting).
FIGS. 4A-F show that the direction of expansion can be controlled
by combining elastic material and strain limiting material into one
monolithic layer, which contains the elastomeric sections and the
radially constraining sections. In some embodiments, the
elastomeric sections and the radially constraining sections are
cast extruding together, or embed fiber reinforcements could be
used to create the strain limiting property. The various
applications and variations described with particularity for the
multilayer versions of the composite layer actuator can also be
achieved using the combined elastomer/strain limiting material
arrangement in a monolithic layer.
In some embodiments, the radially constraining section comprises a
radial strain strip oriented parallel to one of the edges of the
first or second composite layer (see, e.g., FIGS. 4A and 4C).
In other embodiments, the radially constraining section comprises a
radial strain strip oriented at an angle to one of the edges of the
composite layer. For instance, FIG. 4E is an exploded and assembled
view of a soft composite actuator 427 capable of bending and
twisting under fluid pressurization. As illustrated in FIG. 4E, a
monolithic first composite layer 433 is provided, containing
radially constraining sections 431 made of strain limiting
materials and elastomeric sections 429 made of elastic materials.
Sections 431 and 429 are bonded together by thermal, chemical,
and/or mechanical methods to form the monolithic first composite
layer 433. Sections 429 and 431 both have thickness the same as
that of the first composite layer 433. As shown in FIG. 4E, the
radially constraining section 431 is in the form of a radially
constraining strip, which is oriented in an angle (.theta.) with
respect to the layer 433's horizontal edge (shown as the y axis).
.theta. can be in any ranges or have any values. In some
embodiments, .theta. is about 10, 20, 30, 40, 45, 50, 60, 70, 80
degree, or in any ranges bound by any two of the values disclosed
herein. The angled elements, e.g., 431 or 429, in the anisotropic
layer 433 can be evenly spaced, intermittently spaced, and/or at a
gradient of angles. Angling the elastic and strain limited elements
in the anisotropic layer promotes linear growth at an angle to the
y-axis. As a result, when layer 433 is combined with a strain
limiting layer, e.g., 435, the resulting actuator 427 will
simultaneously bend and twist upon actuation.
FIG. 4F is an exploded and assembled view of an actuatable device
capable of linear extension and twisting under fluid pressurization
by bonding two anisotropic layers with angled elastic and strain
limiting elements. A first composite layer 439, containing radially
constraining sections 445 (with an angle .theta. with respect to
the layer 439's horizontal edge) and elastic sections 443, is
combined with a second composite layer 441, which contains similar
elastic section 447 and radially constraining section 449, to form
a soft composite actuator 437. When actuated, soft composite
actuator 437 extends linearly and twists.
In some embodiments, the soft composite actuator stiffens when
actuated and thus can be termed a stiffener. FIG. 5A shows the top
view of an unactuated stiffener soft composite actuator 501 (top
portion of FIG. 5A) and the response of the actuator when actuated
(bottom portion of FIG. 5A) under fluid pressurization. The
radially constraining layer 523 of the actuator 501 contains cutout
section 505 and solid sections 503. In this arrangement, the cut
outs define areas where the actuator is allowed to bend and the
solid sections, e.g., 503, of the radially constraining layer
restrict any actuation by inflating to form a pressurized tube
termed a stiffener.
FIG. 5B is an extension of FIG. 5A demonstrating that several
bending joints 511 can be designed into a single actuator. In this
illustration, the actuator 507 contains solid sections 509 (which
stiffen upon actuation) and cutout sections 511 (which allow the
actuator to bend during actuation) in its radially constraining
layer 519. As a result, this closed loop actuator 507 could be used
to wrap around an object or to create an opening.
FIG. 5C is an extension of FIG. 5A demonstrating that multiple
bending actuators can be combined on a single laminate. In this
figure, actuator 513 contains four individual bending actuators
which are arranged to form a grasping device. The actuator 513 has
a radially constraining layer 517 which contains openings, e.g.,
cutout sections 525 and solid sections 527. The bottom portion of
FIG. 5C shows the scenario where three digits are activated when
the bladder of the actuator is connected to a pressurized fluid
source via a tubing connection, while one is not connected to the
pressurized fluid source or is connected to a different pressurized
fluid source. In this figure, four individual bending actuators are
arranged to form a grasping device. As a result, the three digits
and the fourth digit can be controlled separately.
The locations of the openings, e.g., cutout sections and solid
sections can be adjusted and arranged in any predetermined matter
to achieve a desired actuation, e.g., any preferred ranges of
motion or shapes of the actuated actuator. For example, as shown in
FIG. 4E-4F, the radially constraining sections can be arranged to
be in an angle with respect to the edge of the material layers of
the actuator, which can produce simultaneous bending and twisting
motion (not illustrated).
FIG. 6A depicts a top view and an isometric view of an actuatable
device 605 that combines a multiple functions onto a single
laminate. In this figure, two bending actuators 601 (having cutouts
in its radially constraining layers) are connected via two
stiffeners 603 (having solid sections in its radially constraining
layers). The material layers of the actuator are bonded at
perimeters such as 607. Thus, on a single sheet, multiple functions
can be achieved by using a single bladder. In FIG. 6A, the
rectangular profile of the actuator 605 has a perimeter thermal
bond and a second bond offset a certain distance inward (shown as
607). On two vertical sides (617) of the rectangle the radially
constraining layer has openings, e.g., cutouts that define a
bending actuator while on the other two sides, i.e., the horizontal
sides 619, the radially constraining layer has no openings, e.g.,
cutouts, which under fluid pressurization becomes a stiff inflated
tube that can be used to as a structural element.
FIG. 6B shows an actuator device 615 having multiple stiffeners
used to support bending actuators and achieve greater coverage. In
this figure, two bending actuators 611 (having cutouts in its
radially constraining layers) are connected via four stiffeners 613
(having solid sections in its radially constraining layers). The
material layers of the actuator are bonded at perimeters such as
609. In this embodiment, the actuator can be used to generate a
bending motion with greater coverage. For example this could be
used as a splint that can conform to the leg while also providing
stability (i.e. stiffness) along the length of the injury. In some
embodiments, the single bladder of the actuator can be separated
into multiple bladders for more control over each function of each
section of the actuator device. For example, the stiffeners may
need to be separate bladders from the bending actuator because they
may operate at different pressures.
In some embodiments, the soft composite actuator further comprises
one or more rigid elements attached to the strain limiting layer.
Rigid elements could be added to actuator body to define discrete
bending points or to rigidize certain lengths for improved force
transmission or stability. In some embodiments, rigid elements also
enable a tighter bending radius of curvature and can be used as
mounting substrate for auxiliary equipment.
FIG. 7A depicts an exploded view and cross-section view of an
actuatable device 713 that incorporates rigid elements as an
additional layer. Soft actuator 713 contains a radially
constraining layer 701, an elastic layer 703, a strain limiting
layer 705, and a rigid element layer 707 containing rigid elements
709. These layers are stacked and bonded together to provide the
actuator 713.
FIG. 7B is a side view of the bending actuator 713 under fluid
pressurization with rigid elements where it only bends at the gaps
between the rigid elements, e.g., position 715. FIG. 7B shows the
actuator 713 with the four layers 701, 703, 705, and 707 described
above in FIG. 7A. Upon actuation, a portion of the elastic layer
711 may expand through the openings, e.g., cutouts in the radially
constraining layer 701. In some embodiments, the space between the
rigid elements may be increased to increase the radius of
curvature.
The soft composite actuator as described herein may have a variety
of functions. In some embodiments, the soft composite actuator is
configured to open an incision, move, displace organs, muscle,
and/or bone, brace a joint, be worn to support joint movements,
shape-match an object, fold pre-defined bending joints to create
origami-like structures, achieve a sufficient grasp over the
object, or create a padded layer conformal to the object.
In some embodiments, one of the material layers, e.g., the elastic
layer, is pre-strained before being bonded to the radially
constraining layer and/or the strain limiting layer. Pre-straining
the elastic layer could be used to create a bimorph bending
actuator. This could be used as a way to make graspers that are low
profile when unpressurized and can conform around an object when
pressurized. Any other type of material layer can be pre-strained
as well.
FIG. 8A shows the assembly of a bimorph bending actuator that
incorporates a pre-strained layer during the assembly. The elastic
layer 803 is pre-strained along the directions of 807 and 809,
before being bonded to the radially constraining layer 801 and the
strain limiting layer 805. FIG. 8B shows the range of motion of the
bimorph bending actuator 825 at different stages of pressurization.
Under no fluid pressurization (state 811), the pre-strained elastic
layer causes the actuator 825 start in a curled position. Under
partial fluid pressurization (state 813), the actuator 825 uncurls
and straightens out. When the actuator is fully pressurized (state
815), it curls to the opposite side.
FIG. 8C illustrates that the opposing bimorph bending actuators can
be used to form a grasper 827. At the unpressurized state 817, the
grasper curls and does not grab object 823. At the partially
actuated state 819, the grasper 827 only partially grabs object
823. Finally, when the grasper 827 is fully pressurized (state
821), object 823 is tightly surrounded by the grasper 827.
Similarly a bimorph bending actuator can also be created with two
opposing bending actuators that are bonded together (or share the
same strain limiting layer).
In some embodiments, the soft composite actuator is a
multi-degree-freedom bending actuator. In some specific
embodiments, the degree of the actuation, e.g., bending of the soft
composite actuator may be controlled and fine-tuned by the fluid
pressure inside the bladder. In some embodiments, the soft
composite actuator is attached to one or more pneumatic or
hydraulic connections. For instance, the pneumatic or hydraulic
connections connected to the bladder, e.g., a fluid pump, may apply
different pressures to the fluid so result in different degrees of
actuation, e.g., bending.
FIGS. 9A-9C are an extension of FIG. 4C where multiple linear
extending actuators can be grouped on the same laminate to form a
multi-degree of freedom bending and extending actuator. In these
figures, two anisotropic layers (first composted layer 901 and
second composite layer 903 in FIG. 9B) are bonded together at
locations shown as 911 such that they form three different
bladders, 905, 907, and 909. Each of the first and second composite
layers has elastic sections 913 and radially constraining sections
915. After bonding, three linear actuators, 917, 919, and 921 are
formed.
FIG. 9B is an end view of FIG. 9A (upper portion of FIG. 9B) and
depicts the next stage in the fabrication of a multi-degree of
freedom bending and extending actuator where the laminate is bonded
end to end to form a tube shape (lower portion of FIG. 9B) at end
923.
FIG. 9C illustrates that when one bladder of the actuator is
selectively pressurized it will linearly extend causing the tube
structure to bend to an angle .theta. (scenario 927). Fluid
pressurization of one or more chambers/bladders causes bending and
some linear extension. On the other hand, equal pressurization of
the all the bladders will cause the actuator to only extend
linearly (scenario 929). Note that in scenario 927, only one of the
bladders is pressurized to have a pressure P.sub.1, which is
greater than the outside atmosphere pressure. In scenario 929, all
of the three bladders are equally pressurized to have pressures
P.sub.1, P.sub.2, and P.sub.3, which are greater than the outside
atmosphere pressure.
In some embodiments, the soft composite actuator as described
herein may be used for stabilizing a limb. In some embodiments, the
soft composite actuator is part of a splint or is the splint. In
other embodiments, the soft composite actuator is part of a grasper
comprising a plurality of digits, or is grasper.
FIG. 10 is a perspective view of a wearable application where soft
actuators have been incorporated into a glove 1001 to assist joint
motions. The glove 1001 contains cutouts 1003 in its radially
constraining layer to accommodate the finger joint bending. The
material layer-bonding approach enables the integration of a
network of soft actuators that can apply torques to finger joints
to support hand closing. A similar configuration on the palm side
could assist opening the hand. With this approach, the material
layers can serve a dual function of forming the actuators and
serving as the glove material.
In some embodiments, one of material layers, e.g., the elastomeric
layer, the strain limiting layer, the first and second composite
layer (described below), and/or the radially constraining layer, is
configured to have one or more functions selected from the group
consisting of absorbing fluids, transmitting light, changing color
or luminescence, embedding a soft sensor, embedding a medical
patch, embedding at least a part of an electronic circuit,
embedding a heating element, and a combination thereof.
FIG. 11 is perspective view of a material layer described herein
demonstrating multi-functionality. In some embodiments, any of the
material layers described herein can incorporate electronics,
heating elements, sensors, and so forth. As shown in FIG. 11 (left
portion), a heating element 1105 may be incorporated into a
material layer 1101, e.g., a strain limiting layer. Also shown in
FIG. 11 (right portion), a circuit board or electronic element 1107
can be incorporated (e.g., printed) into a material layer 1103,
e.g., a strain limiting layer. Any of the material layers described
herein can have sensing capabilities by incorporating flex sensors,
inertial measurement units (IMUs), or soft sensors into the
material layers.
FIG. 12 shows a sequence of side views of an actuatable device 1201
that uses connected pressurized bladders to transmit force to lift
an object. In step 1215, the actuator 1201 is formed by bonding
multiple material layers at locations such as 1203. The actuator
1201 has three bladders, 1205, 1207, and 1209, which are in fluidic
communication with one another. In step 1217, a heavy object 1213
is placed on bladder 1207 and pressurized fluid 1211 is infused
into the bladders. Bladders 1205 and 1209 expand however bladder
1207 does not expand due to the gravity force of object 1213. In
step 1219, force F is applied onto bladders 1205 and 1209. The
force F can be applied by human or mechanical means. As a result,
pressurized fluid is forced into bladder 1207 and causes bladder
1207 to expand and at the same time, move object 1213 upwards for a
distance .DELTA.D. Thus, the flexible nature of the material layers
enables the bladder to operate in non-planar scenarios and the
fluid therein can be passed through a narrow opening, e.g., opening
1221.
In some embodiments, the soft composite actuator described herein
can be prepared by bonding a portion of a pre-stacked laminate
containing all the material layers required for the soft composite
actuator. The material layers may be pre-stacked or rolled into a
multi-layer laminate. When in use, a desired size of the laminate
may be removed, e.g., cut, and bonded to form the soft composite
actuator. In some embodiments, two or more portions of the laminate
can be cut and bonded together to form a soft actuating device
including two or more soft actuators descried herein.
In some embodiments, the pre-stacked laminate comprising a first
elastomeric laminate layer, a strain limiting laminate layer, and a
first radially constraining laminate layer. A portion of the
laminate is separated to provide the first elastomeric layer, the
strain limiting layer, and the first radially constraining layer
stacked together. These layers may then be bonded together to
provide a soft composite actuator described herein.
In some embodiments, the pre-stacked laminate comprising a
monolithic, first composite and a strain limiting laminate layer. A
portion of the laminate is separated to provide the first composite
layer and the strain limiting layer stacked together. These layers
may then be bonded together to provide a soft composite actuator
described herein.
FIG. 13A shows a sequence of images where a rolled sheet of
actuatable devices can be cut to a desired length and the bladders
can be resealed with a sealing tool. In step 1301, a plurality of
material layers bonded at locations such as 1311 are rolled into a
roll. During use, a desired portion of the roll can be cut. The
newly cut edge can be sealed using a sealing tool 1313 (step 1303).
The cut portion can be further divided as shown in step 1305, where
the sealed edge 1319 remains sealed.
FIG. 13B illustrates how the cut portion of the material layer roll
can be assembled together to form a range of different actuatable
devices. In step 1307, bending actuator 1321 (which contains
cutouts 1315 in its radially constraining layer) and bending
actuator 1325 (which contains cutouts 1327 in its radially
constraining layer) are joined together to a stiffening actuator
1323 (which contains solid strain limiting sections 1317 in its
strain limiting layer). In step 1309, the resulting actuator device
1329 is actuated where the bending portions (1321 and 1325) of the
device bend, while the stiffening potion (1323) is stiffened. These
illustrations present concepts where sheets of any soft actuator
described herein, e.g., bending, linear extending, contracting,
bend/twist, and stiffening actuators, can be cut to length, sealed,
and assembled into a range of configurations.
In certain embodiments, a packaging for holding the soft composite
actuator's material layer sheet can safely transmit the thermal
bonding pattern without comprising the integrity of the package
seal. In some embodiments, the soft composite actuator's material
layers, e.g., the elastomeric layer, the strain limiting layer, the
radially constraining layer, the first composite monolithic layer,
and/or the second composite monolithic layer, are contained in a
package. Bonding of portions of at least two layers can be achieved
by external means without the compromise of the package to form the
soft composite actuator with predetermined shape. In some
embodiments, the portions of at least two layers are bonded by an
external heat source that passes through the packaging. In other
embodiments, the package further comprises a heating element and
bonding is achieved by heat generated from the activated heating
element. Non-limiting examples of heating element include induction
heating, chemical reaction heating, or electrical heating elements
such as nichrome wire, graphite, and so forth.
FIG. 14 depicts a process by which the bladders of actuatable
devices can be defined while the layers of the laminate are
contained within packaging (both sterile and non-sterile). The
figure depicts packaging that can safely transmit the thermal
bonding pattern without reducing the integrity of the package seal.
This concept presents a solution to meeting inventory needs. In
step 1407, a sterile (or non-sterile) packaging 1403 holds the
material layer sheet 1401 to be thermally bonded. The face of the
packaging may contain a bonding pattern 1405. In step 1409, a
bonding device is used to thermally (or chemically or mechanically)
bond the desired bladder along the thermal bonding pattern 1413
labelled on the face of the packing Thus, in step 1409, thermal
bond pattern (a rectangle in this case) has been transferred to the
contents of the package while still maintaining the sterility of
the package contents. When the soft composite actuator 1415 is
needed, it is removed from the packaging (step 1411).
In yet another aspect, a method of actuation is described,
including: providing a soft composite actuator of any of the
embodiments described herein; and pressurizing the bladder with a
fluid, wherein the soft composite actuator actuates in a
predetermined manner.
In some embodiments, the material layers are arranged and bonded to
create structural anisotropy. In some embodiments, actuation of the
soft composite actuator achieves one or more motions selected from
the group consisting of bending motion, combination bending,
twisting motion, linear extension, a combination of linear
extension and twist, linear contraction, a combination of linear
contraction and twist, and any combination thereof. In some
specific embodiments, the soft composite actuator stiffens upon
fluid pressurization. The bladder may be inflated to different
pressures to achieve a tunable stiffness surface. The different
pressures may be controlled or tuned by the external pressurized
fluid source.
In yet another aspect, a soft actuating device is described,
including a plurality of the soft composite actuators described in
any of the embodiments herein. The plurality of the soft composite
actuators may be connected to the same fluid source, or to two or
more different fluid source. In certain embodiments, the soft
actuating device includes a first and a second soft composite
actuators described in any of the embodiments herein. The first
soft actuator may be connected to a first pressurized fluid source
and the second soft actuator may be connected to a second
pressurized fluid source. Thus, the first and the second soft
composite actuators may be actuated separately or alternately, by
alternately actuating the first and second fluid sources. In some
specific embodiments, the first soft actuator is a stiffener
described herein. In some specific embodiments, the second soft
actuator is a bending actuator described herein. Thus, the soft
actuating device may be controlled to enable different motions,
e.g., bending or stiffening, by actuating different fluid sources
connected to the bladders of the individual soft composite
actuators in the soft actuating device.
In yet another aspect, a method of making a soft composite actuator
according to any of the embodiments described herein is disclosed,
including: providing a first elastomeric layer, a strain limiting
layer, and a first radially constraining layer; wherein the
elastomeric layer is disposed between the radially constraining
layer and the strain limiting layer; and bonding the first
elastomeric layer, the strain limiting layer, and the first
radially constraining layer to form sealed parameters defining at
least one bladder for holding pressurized fluid.
In some embodiments, providing a first elastomeric layer, a strain
limiting layer, and a first radially constraining layer comprises
providing a pre-stacked laminate comprising a first elastomeric
laminate layer, a strain limiting laminate layer, and a first
radially constraining laminate layer; and separating part of the
laminate to provide the first elastomeric layer, the strain
limiting layer, and the first radially constraining layer stacked
together. Thus, the material layers of the soft composite actuator
may be pre-stacked and cut and bond when needed.
In yet another aspect, a method of making a soft composite actuator
according to any of the embodiments described herein is disclosed,
including: providing the first composite layer described herein and
the strain limiting layer; and bonding portions of the first
composite layer and the strain limiting layer to form sealed
parameters defining at least one bladder for holding pressurized
fluid. In some embodiments, the strain limiting layer includes a
second composite layer described herein.
In some embodiments, providing the first composite layer and the
strain limiting layer comprises: providing a pre-stacked laminate
comprising a first composite laminate layer and a strain limiting
laminate layer; and separating part of the laminate to provide the
first composite layer and the strain limiting layer stacked
together.
The bonding may be achieved by a method selected from the group
consisting of thermal method, chemical method, mechanical method,
and a combination thereof. In some embodiments, the method further
includes removing excess material from the soft composite actuator
after bonding.
In yet another aspect, a method of using the soft actuator of any
one of the embodiments for one or more functions is described,
wherein the function is selected from the group consisting of
distribute forces, mixing material, handling material, lifting,
grasping, steering a photovoltaic cell or a mirror, steering
material on a surface.
In some embodiments, steering material on a surface comprises
moving liquid around or moving a solid object.
While for purposes of illustration, embodiments of this invention
have been shown and described, other forms thereof will become
apparent to those skilled in the art upon reference to this
disclosure and, therefore, it should be understood that any such
departures from the specific embodiment shown and described are
intended to fall within the spirit and scope of this invention.
* * * * *